The Dicenomicon has been completely re-architected and largely re-written from the ground up. The Dicenomicon was originally written for iOS 2.0 and was on the AppStore shortly after it opened. A lot has changed since then, but there was still special code designed to support older version of the OS, with code that still worked, but has been superseded with better ways of doing things years ago. And to truly be able to support the new features found in modern version of iOS, that code had to go (not to mention features that were possible but not practical in earlier versions of iOS)
This new version of The Dicenomicon is designed to support the latest features - including support for varying sizes of iOS devices (not just a single iPhone, or even iPhone/iPad/taller iPhone), and system features like iCloud Drive, and split screen multi-tasking. Internally, it is built using storyboards, frameworks, auto-layout, adaptive layout, collection views, page view controllers, and even is being slowly migrated to Swift. All of these things require newer versions of development tools (Xcode), and ultimately, dropping support for older versions of iOS (it currently supports iOS 8 or newer only, since Xcode 8 is required for development with iOS 10 but it only allows targeting back to support iOS 8 - this may be moved to iOS 9 for feature specific reasons if need be).
Specifically, new features include:

iCloud Drive support (as well as general third party storage support, replacing DropBox specific code)

64 bit code

Multiple size devices, from the small “S” series all the way up to iPad Pros

New UI layout - backgrounds are more flexible and features are unified

Multitasking support

Accessories are now small movable palettes with new capabilities

Backgrounds are more flexible (and can be expanded to support a wider range of utilities)

Much more flexible “game room” system (to the point where one could, in theory, have multiple dice views with different game rooms all active at once - though that would have such a horrendous user experience it wouldn’t be practical)

There is still a lot of major functionality not converted/updated yet (such as the custom formula editor or character sheets) and some fairly annoying but, but the new features are pretty cool. I've got a few more major "hassle" level bugs to deal with but user testing via TestFlight should begin next week (depending on how fast it goes through TestFlight approval).

And more good news: If you're reading this, there's a good chance you'll get an email inviting you to test (if you've sent me email before, or made an account and posted in these forums, you'll be asked to be part of the beta test procedure)

You know I'm in. In fact, just pulled up Dicenomicon on my iPhone and got a message saying “Dicenomicon may slow down your iPhone. The developer of this app needs to update it to improve its compatibility.”